Fabric touch sensor and method of manufacture

Abstract

A fabric touch sensor for providing positional information related to a touched region/points. The improved electrographic touch sensor (10) is fabricated using at least one resistive fabric layer (12) in the form of conducting threads. This fabric is constructed using either unidirectional threads (16) or crossed threads (16, 18) formed by overlaying one set with another or weaving the two sets together. The fabric (12) is separated from a second resistive layer (14) to prevent unintentional contact, with separators (24) in the form of non-conducting threads (42), insulator dots (24), or with an air gap. In a preferred embodiment, both resistive layers are fabrics (12, 14) formed from conductive threads. Prevention of Moire-type visual patterns is achieved by orienting the threads in one fabric layer at an oblique angle to those of the second fabric layer. This sensor results in ease of fabrication, reduction of cost, reduction of parallax and eliminates substrate problems associated with those sensors employing the same. No preforming is required to adapt this sensor to a contoured object (36) when both resistive layers are fabric.

We claim: 
     
       1. An electrographic sensor for providing positional information related to a selected point/region touched by a user, which comprises: a first sheet, capable of having electrical potentials introduced therein, extending across such sensor, said first sheet defining a perimeter;   a further sheet, capable of having electrical potentials introduced therein, extending across such sensor, said further sheet defining a perimeter substantially conforming to said perimeter of said first sheet;   separator means interposed between said first and further sheets for preventing contact between said first and further sheets until such sensor is touched by such user at such selected point/region;   means for generating orthogonal electrical potentials within such sensor in X and Y directions whereby such positional information is provided in the form of electrical signals corresponding to X- and Y-coordinates of such selected point/region touched by such user; and   wherein at least one of said first and further sheets is fabricated from a plurality of crossed electrically conductive threads forming a fabric.   
     
     
       2. The sensor of claim 1 wherein said electrically conductive threads are oriented orthogonally in said sheet. 
     
     
       3. The sensor of claim 1 wherein said electrically conductive threads are woven into said fabric. 
     
     
       4. The sensor of claim 1 wherein both said first and further sheets are fabric sheets fabricated from a plurality of crossed electrically conductive threads. 
     
     
       5. The sensor of claim 4 wherein said electrically conductive threads of said first sheet are oriented orthogonally in said first sheet, and said electrically conductive threads of said further sheet are oriented orthogonally in said further sheet. 
     
     
       6. The sensor of claim 4 wherein said electrically conductive threads are woven into said fabric in each of said first and further sheets. 
     
     
       7. The sensor of claim 5 wherein said electrically conductive threads of said first sheet are oriented at a selected angle with respect to said electrically conductive threads of said further sheet. 
     
     
       8. The sensor of claim 4 wherein electrically conductive threads are stretched taut on such sensor and said separator means comprises an air gap between said first and further sheets. 
     
     
       9. The sensor of claim 4 wherein said separator means comprises non-conductive threads oriented unidirectionally between said first and further sheets. 
     
     
       10. The sensor of claim 9 wherein said electrically conductive threads of said first and further sheets have a resistivity of about 10 4  to 10 9  ohms per inch, a diameter of about 0.001 to 0.01 inches and a spacing of about 0.005 to 0.1 inches. 
     
     
       11. The sensor of claim 1 wherein said separator means comprises non-conductive threads oriented unidirectionally between said first and further sheets, said non-conductive threads having a diameter of about 0.002 to 0.01 inches and a spacing of about 0.1 to 0.3 inches. 
     
     
       12. The sensor of claim 7 wherein said selected angle of orientation between threads of said first sheet and threads of said further sheet is chosen to substantially eliminate Moire-type interference patterns. 
     
     
       13. The sensor of claim 12 wherein said selected angle is about 35 to 40 degrees. 
     
     
       14. The sensor of claim 1 wherein one of said first and further sheets is a fabric sheet fabricated from crossed electrically conductive threads, and the remaining sheet comprises a uniformly distributed layer of a resistive substance. 
     
     
       15. The sensor of claim 14 wherein said remaining sheet comprises a substrate and a uniformly distributed resistive coating applied to a surface of said substrate disposed toward said fabric sheet. 
     
     
       16. The sensor of claim 15 wherein said separator means comprises a distribution of insulator dots applied to said resistive coating. 
     
     
       17. An electrographic sensor for providing electrical signals related to a selected point/region touched by a user, which comprises: a first fabric sheet fabricated from electrically conductive threads, said first fabric sheet defining a rectangular perimeter having pairs of opposite edges;   a second fabric sheet, said fabric of said second sheet fabricated from electrically conductive threads, said second fabric sheet defining a rectangular perimeter conforming to said perimeter of said first fabric sheet having pairs of opposite edges;   a first pair of electrode units attached to said first fabric sheet, each one of said first pair of electrode units attached to a pair of opposite edges of said first fabric sheet;   a second pair of electrode units attached to said second fabric sheet each one of said second pair of electrode units attached to a pair of opposite edges of said second fabric sheet, said second pair of electrode units oriented orthogonally to said first pair of electrode units; and   separator means interposed between said first and second fabric sheets for preventing contact between said sheets until such sensor is touched by such user at such selected point/region.   
     
     
       18. The sensor of claim 17 wherein said threads of said first and second fabric sheets are woven to form said sheets, said threads having a resistivity of about 10 4  to 10 9  ohms per inch, a diameter of about 0.001 to 0.01 inches, and a spacing between threads of about 0.005 to 0.1 inches; and wherein said electrode units are bar electrodes extending along said opposite edges. 
     
     
       19. The sensor of claim 17 wherein said separator means comprises an air gap and said threads of said first and second fabric sheets are taut to maintain said air gap. 
     
     
       20. The sensor of claim 17 wherein said separator means comprises a network of unidirectional non-conductive threads, said non-conductive threads having a diameter of about 0.002 to 0.01 inches, and a spacing between threads of about 0.1 to 0.3 inches. 
     
     
       21. The sensor of claim 17 wherein said first fabric sheet is fabricated from a first and a second set of electrically conductive threads, said first set oriented substantially perpendicular to said second set; said second fabric sheet is fabricated from a first and a second set of electrically conductive threads, said first set oriented substantially perpendicular to said second set; and where said first set of threads of said first fabric sheet are oriented at a selected angle to said first set of threads of said second fabric sheet, said selected angle being sufficient to substantially eliminate Moire interference patterns. 
     
     
       22. The sensor of claim 17 wherein spacing between said threads in said first sets within said first and second sheets is greater than spacing between said second sets. 
     
     
       23. An electrographic sensor for providing electrical signals related to a selected point/region touched by a user, which comprises: a first woven fabric sheet fabricated from perpendicularly oriented threads having a resistivity of about 5×10 4  ohms per inch, a diameter of about 0.002 inches and a spacing of about 0.05 inch, said first fabric sheet defining a rectangular perimeter having pairs of opposite edges;   a second woven fabric sheet fabricated from perpendicularly oriented threads having a resistivity of about 5×10 4  ohms per inch, a diameter of about 0.002 inches and a spacing of about 0.05 inch, said second fabric sheet defining a rectangular perimeter having pairs of opposite edges conforming to said edges of said first fabric sheet, said second woven fabric sheet positioned whereby threads of said second woven fabric sheet are oriented at an angle of about 35 degrees to threads of said first woven fabric sheet;   separator means interposed between said first and second fabric sheets, said separator means fabricated of unidirectional non-conducting threads having a diameter of about 0.005 inches and a spacing of 0.2 inches;   a first pair of bar electrodes attached to said first woven fabric sheet, each one of said first pair of bar electrodes positioned at an opposite pair of said edges; and   a second pair of bar electrodes attached to said second woven fabric sheet, each one of said second pair of bar electrodes positioned at an opposite pair of said edges of said second sheet, said second pair of bar electrodes oriented orthogonally to said first pair of bar electrodes.   
     
     
       24. An electrographic sensor for overlying a lighted display for providing electrical signals corresponding to positional information related to a selected point/region touched by a user, which comprises: a first fabric sheet capable of having electrical potentials introduced therein extending across such sensor, said first sheet defining a perimeter and being fabricated from first and second sets of electrically conductive threads, said first set and said second set oriented perpendicularly, said threads having a resistivity of about 10 4  to 10 9  ohms per inch, a diameter of about 0.001 to 0.01 inch and a spacing of about 0.005 to 0.1 inches said first sheet having a first surface for contact with such lighted display and a second surface;   a second fabric sheet capable of having electrical potentials introduced therein extending across such sensor, said second sheet defining a perimeter and being fabricated from first and second sets of electrically conductive threads, said first set and said second set oriented perpendicularly, said threads having a resistivity of about 10 4  to 10 9  ohms per inch, a diameter of about 0.001 to 0.01 ohms per inch, and a spacing about 0.005 to 0.1 inches, said second sheet having a first surface and a second surface disposed toward said second surface of said first sheet;   said first set of threads of said second fabric sheet oriented at a selected angle to said first set of threads of said first fabric sheet to substantially eliminate Moire-type interference patterns;   means attached to such sensor for generating orthogonal electrical potentials within such sensor in X and Y directions, and for obtaining such electrical signals corresponding to positional information when such user touches such sensor at such selected point/region causing contact between said first and second fabric sheets;   separator means interposed between said second surfaces of said first and second fabric sheets to prevent contact therebetween except when such sensor is touched by such user at such selected point/region, said separator means fabricated from unidirectional non-conducting threads having a diameter of about 0.002 to 0.01 inches and a spacing of about 0.1 to 0.3 inches; and   a transparent overlay disposed on said first surface of said second fabric sheet.   
     
     
       25. A method of manufacturing an electrographic sensor for providing positional information related to a selected point/region touched by a user, which method comprises: fabricating a thin rectangular insulating frame defining a perimeter and a central open area conforming to an active area of such sensor, said frame having a vertical and horizontal orientation;   securely mounting an insulating thread upon said frame in horizontal rows, said insulating thread having a diameter of about 0.002 to 0.01 inches, and each row being spaced apart about 0.1 to 0.3 inches;   winding a first conductive thread vertically around said frame in substantially parallel rows, said first conductive thread having a resistivity of about 10 4  to 10 9  ohms per inch, a diameter of about 0.001 to 0.01 inches, and a spacing between rows of about 0.005 to 0.1;   winding a second conductive thread horizontally around said frame in substantially parallel rows, said second conductive threads having a resistivity of about 10 4  to 10 9  ohms per inch, a diameter of 0.001 to 0.01 inches and a spacing between rows of about 0.005 to 0.1 inches thereby forming with said rows of said first and second conductive threads first and second fabric sheets separated by said insulating threads;   fastening said first and second conductive threads to said frame;   severing connections between said first and second fabric sheets at said perimeter of said frame; and   attaching electrodes to said first and second fabric sheets whereby orthogonal electric fields can be produced within such sensor.   
     
     
       26. An electrographic sensor for providing electrical signals related to a selected point/region touched by a user, such sensor adapted to retrofit on a video display tube having a bezel with an opening which comprises: an open frame adapted to be closely received within such opening of such bezel, said frame having two pairs of opposite side walls joined at corners, each of said walls having a contour along one edge to substantially match a face contour of such video display tube;   a first fabric sheet fabricated from electrically conductive threads stretched taut across said frame at said contoured edges and extended up and attached to outside surfaces of one pair of opposite side walls;   a second fabric sheet fabricated from electrically conductive threads stretched taut across said frame at said contoured edges and extended up and attached to outside surfaces of a second pair of opposite side walls;   separator means interposed between said first and second fabric sheets to prevent contact between said first and second fabric sheets until such sensor is touched by such user at such selected point/region; and   electrode means attached to at least one of said fabric sheets for the application of electrical potentials to produce orthogonal electrical fields within such sensor whereby electrical signals corresponding to X- and Y-coordinates of such selected point/region are generated when such sensor is touched by such user.   
     
     
       27. The sensor of claim 26 wherein said separator means is an array of nonconductive threads stretched taut across said frame. 
     
     
       28. The sensor of claim 26 wherein said electrode means comprises: a first pair of electrode units, each one of said first pair of electrode units attached to said first fabric sheet along said outside surface of said one pair of opposite side walls of said frame; and   a second pair of electrode units, each one of said second pair of electrode units attached to said second fabric sheet along said outside surface of said second pair of opposite side walls of said frame.   
     
     
       29. The sensor of claim 26 wherein said threads of said first fabric sheet are oriented at a selected angle to said threads of said second fabric sheet, said selected angle being sufficient to substantially eliminate Moire interference patterns. 
     
     
       30. The sensor of claim 26 wherein said threads of said first and second fabric sheets have a resistivity of about 10 4  to 10 9  ohms per inch, a diameter of about 0.001 to 0.01 inches, and a spacing between threads of about 0.005 to 0.1 inches; and wherein said nonconductive separator threads have a diameter of about 0.002 to 0.01 inches, and a spacing between said nonconductive threads of about 0.1 to 0.3 inches. 
     
     
       31. An electrographic sensor for providing positional information related to a selected point/region touched by a user, which comprises: a first sheet, capable of having electrical potentials introduced therein, extending across such sensor, said first sheet defining a perimeter;   a further sheet, capable of having electrical potentials introduced therein, extending across such sensor, said further sheet defining a perimeter substantially conforming to said perimeter of said first sheet;   separator means interposed between said first and further sheets for preventing contact between said first and further sheets until such sensor is touched by such user at such selected point/region;   means for generating orthogonal electrical potentials within such sensor in X and Y directions whereby such positional information is provided in the form of electrical signals corresponding to X- and Y-coordinates of such selected point/region touched by such user; and   wherein at least one of said first and further sheets is a fabric sheet fabricated from a plurality of crossed electrically conductive threads oriented orthogonally in said fabric sheet.